Is taking 50000 iu d2 pill 1/week for month safe, esp along with 300 mg wellbutrin (bupropion) xl (morn) & 1.5 mg klonopin plus 1 mg melatonin (night)?

Vit D very safe: Yes, that high dose of vitamin D (50,000 IU) is often used weekly for up to 12 weeks to quickly replenish someone's vitamin D that is low. It has no noticeable side effects and doesn't interact with the medications you mentioned. No worries.

Pretty safe.: That is the recommended dose for that vitamin D. There is not an obvious interaction between any of the drugs except for klonapin and melatonin (they both make one sleepy) and the interaction there is quite mild. Klonapin is a controlled dangerous substance with addictive potential.